A polarizer that is manufactured by stretching a polyvinyl alcohol resin (hereafter referred to as a “PVA resin”) can be easily divided or broken in a stretching direction. Because of this, in general, instead of being used by itself as a unit, a polarizer is used in a form of an optical film laminate, both sides of which have a polarizer protection functional layer formed thereon for protecting the polarizer and improving durability. In general, a transparent protection film, such as triacetylcellulose (TAC), is used for the polarizer protection functional layers. There are cases in which an optical film laminate is used in which the durability is further improved by laminating a layer having an ultraviolet ray absorption function, a hard coating layer, or the like on a protection film. Recently, there are cases in which a phase difference film for optical compensation is used as a polarizer protection functional layer.
In general, a unit for an image display device, which is used for an image display device, bonds such an optical film laminate to a substrate of a panel for an image display device via a layer of agglutinant. An agglutinant that is used when a panel for an image display device and an optical film laminate are bonded together can be defined so as to have the following characteristics.                It has high viscosity and is a semisolid substance with a low elastic modulus. By adding pressure, it is bonded with a body to be adhered.        Even after bonding, it can be exfoliated from the body to be adhered.        The state of the agglutinant does not change in the bonding step.        
An agglutinant with such characteristics is one type within a broad range of adhesives. As the agglutinant exists between two bodies to be adhered and pressure is added, adhesive strength is manifested. Thus, it is also called a “pressure-sensitive adhesive.” In this specification, “agglutinant” refers to such a “pressure-sensitive adhesive.”
Incidentally, as described above, a conventional optical film laminate generally includes a polarizer and a polarizer protection functional layer on both surfaces of the polarizer. However, if the polarizer protection functional layer could be attached to only one surface, an optical film laminate could be made thinner. Using such a polarizer protection functional layer for one surface in the manufacture of an image display device would reduce the number of materials and reduce the cost, due to the optical film laminate being made thinner. Thus, as the size of today's image display devices becomes large and their thickness becomes thinner, this would be extremely advantageous in terms of the environment and the cost.
However, a polarizer that is formed by stretching a hydrophilic PVA resin has high hygroscopicity, and expansion and contraction are easily generated due to the changes in temperature and humidity. Because of this, when such a protection optical film laminate for one surface and a panel for an image display device are bonded by agglutinant, dimensional changes in the optical film laminate are generated due to changes in heat, humidity, and/or rapid temperature changes. Because of this, there is a possibility that there might be a crack in the optical film laminate, or that the optical film laminate and the panel for an image display device may be exfoliated. Thus, in current technology of manufacturing an image display device using agglutinant, it is difficult to implement a protection optical film laminate in which a protection functional layer is laminated only to one surface of a polarizer.
As a technology that suppresses a crack from being generated in a single protection optical film laminate, a technology is proposed in which a coating layer is formed on a surface of a polarizer on which a protection functional layer is not laminated (for example, Japanese Patent 4306269 (Patent Reference 1)). However, because the polarizer is protected by an extremely thin coating layer, compared to the thickness of the protection functional layer, such an optical film laminate can be used for a small image display device for a mobile [device], but when it is used for a large image display device that is recently demanded, necessary durability against cracking cannot be obtained.
A disadvantage in a technology of bonding a panel for an image display device and an optical film laminate with agglutinant is considered to be solvable by bonding a panel for an image display device and an optical film laminate with adhesive instead of agglutinant. For this, a technology is also proposed. An example of such a technology is Japanese Published Patent Application 2010-286764 (Patent Reference 2).
A technology of Patent Reference 2 relates to an optical laminate in which (i) a liquid crystal panel substrate and (ii) a polarization film in which a transparent protection layer is laminated only to one side are laminated via an adhesive layer therebetween, the adhesive layer comprising an active energy ray curing resin composition including an epoxy compound. According to Patent Reference 2, an optical laminate in which a polarization film and a liquid crystal panel are laminated via adhesive is excellent in thinness, lightness, and durability. However, additional testing by the inventors of this invention confirms that in the optical laminate of Patent Reference 2, an end portion of a polarization film is exfoliated from a liquid crystal panel when the size is large. Additionally, in such an optical laminate, in order to cure an epoxy-based adhesive, an acid generating agent is used, which has a function of generating acid by light, heat, or the like. Because of this, there is a problem that the adhesive layer directly contacts a surface of a polarizer on which a transparent protection layer is not arranged and that an optical characteristic of the polarizer deteriorates due to the effects of the acid. Furthermore, in general, an optical laminate using an epoxy-based adhesive needs a heating step of approximately several tens of minutes (post-curing) after light radiation, so productivity is low, which causes a problem.
Additionally, in this specification, adhesive is used so as to be distinguished from the above agglutinant and can be defined as a substance with the following characteristics.                Adhesive is originally a liquid with low viscosity having flowability, makes a contact area large by sufficiently wetting body to be adhered when it is coated onto body to be adhered, and is bonded with the body to be adhered by curing with light irradiation or heat.        By increasing the light irradiation amount or heat amount, the adhesive passes through an adhesion state and is cured.        After bonding, the body to be adhered and the adhesive layer cannot be exfoliated without breaking agglomeration of the body to be adhered and/or the adhesive layer.        An adhesive state irreversibly changes in a bonding step (changes from liquid to solid).        
Adhesive with such characteristics is energy curing type adhesive that manifests adhesive strength by curing the adhesive by applying energy such as light or heat to it. Depending on the type of energy to be applied, it is called, for example, “ultraviolet ray curing type adhesive,” “heat curing type adhesive,” or the like.